Need help installing addon on mac
Blender searches for addons in three places, one of which is /Users/{user}/Library/Application Support/Blender/2.72/. If your addon is already there, then it is "installed".
The install from file button in the user preferences essentially just copies files into this directory.

If you don't see the addon listed in the user preferences, then there may be something wrong with the addon. Try starting blender from a terminal and see if there are any error messages.